Double Worm Speed Reducers Market Outlook

The global market size for Double Worm Speed Reducers was valued at approximately USD 1.2 billion in 2023 and is projected to reach USD 2.1 billion by 2032, growing at a compound annual growth rate (CAGR) of 6.2% during the forecast period. This robust growth is driven by the increasing demand for efficient power transmission solutions across various sectors such as manufacturing, automotive, and aerospace. The enhanced precision and reliability offered by double worm speed reducers are key factors boosting their adoption.

One significant growth factor in the double worm speed reducers market is the rising automation in industrial machinery. Industries are increasingly automating their processes to improve productivity and reduce labor costs. Double worm speed reducers play a crucial role in these automated systems by providing precise speed reduction and torque multiplication, which are vital for the smooth operation of machinery. Additionally, the increasing focus on energy efficiency and the need to minimize operational downtime are propelling the demand for these reducers.

Another pivotal driver is the growing automotive industry, which extensively uses speed reducers in various applications, such as power steering systems and electric vehicle drivetrains. With the automotive sector witnessing a surge in electric vehicle production, the demand for high-efficiency, compact, and reliable speed reducers is on the rise. Moreover, advancements in materials and manufacturing technologies have led to the development of lighter and more durable double worm speed reducers, making them an attractive choice for automotive manufacturers.

The aerospace sector also contributes significantly to the market growth. The need for high-precision components in aircraft systems necessitates the use of reliable speed reducers. Double worm speed reducers are preferred in aerospace applications due to their ability to provide smooth and stable motion control, essential for various aircraft systems. With the aerospace industry continually expanding and upgrading its fleet, the demand for advanced speed reducers is expected to grow steadily.

From a regional perspective, the Asia Pacific region holds a substantial market share and is anticipated to dominate the market during the forecast period. This dominance is attributed to the rapid industrialization and the presence of major manufacturing hubs in countries like China, India, and Japan. Moreover, North America and Europe are also expected to witness significant growth due to the strong presence of automotive and aerospace industries. These regions' emphasis on technological advancements and the adoption of automation further contribute to the growth of the double worm speed reducers market.

Type Analysis

The double worm speed reducers market is segmented into two primary types: Single Reduction and Double Reduction. The Single Reduction type is characterized by a single stage of reduction, offering a simpler design and lower cost. This type is particularly favored in applications where space and budget constraints are critical, and only moderate speed reduction is required. Single Reduction speed reducers are commonly used in basic industrial machinery and light-duty applications where efficiency and compactness are prioritized over extensive speed reduction capabilities.

On the other hand, Double Reduction speed reducers involve two stages of reduction, providing a greater level of torque multiplication and speed reduction. This type is essential in applications that demand substantial torque and precise speed control, such as heavy industrial machinery, automotive drive systems, and aerospace components. The double reduction mechanism allows for higher efficiency and more robust performance in demanding environments. As industries continue to evolve and require more sophisticated machinery, the demand for Double Reduction speed reducers is projected to rise significantly.

The increasing complexity of industrial processes necessitates the use of Double Reduction speed reducers to manage high-torque requirements while maintaining efficiency. This trend is particularly evident in heavy industries such as mining and construction, where machinery must operate under extreme conditions and require reliable power transmission solutions. The ability of Double Reduction speed reducers to provide smooth and consistent performance under load makes them indispensable in these sectors.

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The full text of this article can be freely accessed on the publisher's website.

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Parallel-Shaft Helical Gear Reducer Market Outlook

The global market size for Parallel-Shaft Helical Gear Reducers was valued at approximately USD 4.7 billion in 2023 and is forecasted to reach USD 7.6 billion by 2032, growing at a CAGR of 5.2% during the forecast period. The sustained growth in this sector can be attributed to the increasing demand for energy-efficient machinery and the rising industrialization in emerging economies.

One of the primary growth factors propelling the Parallel-Shaft Helical Gear Reducer market is the surge in industrial automation. As industries aim to enhance operational efficiency, the demand for precise and reliable gear systems has increased. Parallel-shaft helical gear reducers are known for their high efficiency and ability to handle heavy loads, making them ideal for automated machinery. Additionally, advancements in gear technology, such as improved materials and manufacturing techniques, have enhanced the performance and lifespan of these reducers, further driving market growth.

Another significant growth driver is the expanding construction and infrastructure sector. With the rise in urbanization and infrastructure development projects worldwide, there is a growing need for robust machinery. Parallel-shaft helical gear reducers are extensively used in construction machinery due to their ability to transmit high torque and their reliability under heavy-duty conditions. As countries invest in large-scale infrastructure projects, the demand for these gear reducers is anticipated to rise significantly.

The automotive industry's growth also significantly contributes to the market's expansion. Parallel-shaft helical gear reducers are integral components in various automotive applications, including powertrains and auxiliary systems. With the automotive industry shifting towards electric vehicles (EVs), the need for efficient and reliable gear systems has become more critical. The ongoing R&D in the automotive sector to develop advanced gear systems is expected to create lucrative opportunities for market players.

From a regional outlook perspective, Asia Pacific holds the largest market share and is expected to maintain its dominance during the forecast period. The region's rapid industrialization, coupled with significant investments in infrastructure and automotive sectors, has fueled the demand for parallel-shaft helical gear reducers. Countries like China and India, with their expanding manufacturing bases, are key contributors to the market's growth. Additionally, favorable government policies promoting industrial growth and energy-efficient machinery usage further bolster the market in this region.

Product Type Analysis

The Parallel-Shaft Helical Gear Reducer market is segmented by product type into Single Reduction, Double Reduction, and Triple Reduction. Each type offers specific advantages and is chosen based on the application requirements.

Single Reduction gear reducers are designed for applications requiring a moderate reduction ratio. They are widely used across various industries due to their simplicity and cost-effectiveness. These gear reducers are particularly favored in applications where high efficiency and compact design are crucial. They provide a straightforward solution for many machinery setups, contributing to their significant market share.

Double Reduction gear reducers offer higher torque and reduction ratios compared to single reduction types. They are commonly used in more demanding applications that require significant torque transmission. Industries such as construction and mining, where equipment must handle heavy loads under tough conditions, predominantly use double reduction gear reducers. Their ability to provide enhanced torque without compromising on efficiency makes them a popular choice.

Triple Reduction gear reducers are designed for applications that require very high reduction ratios and torque capacities. These are typically used in heavy-duty industrial applications such as power generation and large-scale manufacturing processes. Their complex design allows for significant torque multiplication while maintaining operational efficiency. The increased industrial activity and the need for powerful machinery drive the demand for triple reduction gear reducers.

The choice between these types depends heavily on the specific requirements of the application, such as the desired reduction ratio, space constraints, and the nature of the load bei

Automotive Final Reduction Drive Market Outlook

The global automotive final reduction drive market size was valued at approximately USD 4.1 billion in 2023 and is projected to reach around USD 6.2 billion by 2032, growing at a CAGR of 4.5% during the forecast period. The market growth is primarily driven by the increasing demand for efficient power transmission systems in vehicles, technological advancements, and the rising production of automobiles globally.

One of the significant growth factors for the automotive final reduction drive market is the increasing focus on fuel efficiency and emission regulations. Governments worldwide are implementing stringent norms to reduce carbon emissions, which has pushed automotive manufacturers to adopt advanced drivetrain components that offer better fuel efficiency. The final reduction drive, being a crucial component in the transmission system, plays a vital role in enhancing vehicle performance and fuel economy. As a result, the demand for efficient final reduction drives is on the rise.

Another contributing factor is the growing adoption of electric vehicles (EVs). With the global transition towards electric mobility, the need for specialized final reduction drives designed for EVs has increased. These drives are essential for managing the high torque and power requirements of electric motors. The rise in EV production and sales, particularly in regions like North America and Europe, is expected to significantly boost the demand for final reduction drives tailored for electric vehicles, thereby driving market growth.

The rapid development of automotive technology also plays a pivotal role in market expansion. Innovations such as advanced driver-assistance systems (ADAS), autonomous driving technology, and connected vehicles necessitate efficient and reliable power transmission systems. The final reduction drive, being a critical component in ensuring smooth power delivery to the wheels, is witnessing increased adoption to support these advanced automotive technologies. The continuous R&D efforts by manufacturers to enhance the performance and durability of final reduction drives are further propelling the market forward.

From a regional perspective, Asia Pacific holds a significant share of the automotive final reduction drive market, driven by the high production and sales of automobiles in countries like China, Japan, and India. The region's growing automotive industry, coupled with increasing investments in electric vehicle infrastructure and technological advancements, is expected to sustain its market dominance. North America and Europe are also key regions, with substantial contributions from their well-established automotive sectors and increasing focus on electric vehicles.

Product Type Analysis

The automotive final reduction drive market is segmented into single reduction drives and double reduction drives based on product type. Single reduction drives are commonly used in passenger cars and light commercial vehicles due to their simplicity and efficiency. These drives offer a straightforward design with fewer components, which translates to lower manufacturing costs and ease of maintenance. The demand for single reduction drives is expected to remain robust, driven by their widespread application in conventional vehicles.

Double reduction drives, on the other hand, are designed to handle higher torque and power requirements, making them suitable for heavy-duty commercial vehicles and specific electric vehicle applications. The double reduction mechanism provides an additional gear reduction stage, which enhances torque multiplication and load-carrying capacity. As the market for commercial vehicles and high-performance electric vehicles grows, the demand for double reduction drives is anticipated to increase, driven by their superior performance capabilities.

Technological advancements are playing a crucial role in the development of both single and double reduction drives. Manufacturers are focusing on innovations to improve the efficiency, durability, and noise reduction of these drives. The integration of advanced materials and manufacturing techniques is also contributing to the enhanced performance of final reduction drives. Continuous R&D efforts are expected to introduce more advanced products, catering to the evolving needs of the automotive industry.

The market for double reduction drives is expected to witness higher growth compared to single reduction drives, primarily due to the increasing production of

The parallel drive axle market is experiencing robust growth, driven by the increasing demand for electric and hybrid vehicles across passenger and commercial segments. The shift towards fuel efficiency and improved vehicle performance is a major catalyst. While precise market size figures aren't provided, considering a global automotive market valued in the trillions and the significant role axles play, a reasonable estimate for the 2025 parallel drive axle market size could be in the range of $15-20 billion USD. This substantial market is further segmented by axle type (single reduction parallel drive axle, double reduction parallel drive axle, and others), with double reduction axles gaining traction due to their enhanced load-carrying capacity and suitability for heavy-duty vehicles. The market's growth is fueled by technological advancements, including the integration of lightweight materials and improved designs for increased efficiency and durability. Leading manufacturers like Dana Incorporated, ZF Friedrichshafen AG, and Schaeffler AG are driving innovation and expanding their product portfolios to cater to diverse vehicle applications and regional demands. Growth is geographically dispersed, with regions like Asia Pacific (particularly China and India) experiencing rapid expansion due to burgeoning automotive industries. North America and Europe maintain significant market shares due to established automotive manufacturing bases and a high adoption rate of advanced vehicle technologies. However, stringent emission regulations and increasing material costs pose challenges to market expansion. The forecast period (2025-2033) anticipates continued expansion, with a projected Compound Annual Growth Rate (CAGR) likely within the range of 5-7%. This growth trajectory is supported by the ongoing electrification of the automotive sector and the increasing demand for commercial vehicles, especially in developing economies. The competitive landscape is characterized by both established players and emerging innovative companies. Strategic partnerships, mergers, and acquisitions are expected to reshape the market dynamics in the coming years, enhancing technological advancements and expanding market reach. Specific regional growth will depend on factors like infrastructure development, government policies promoting sustainable transportation, and the overall economic growth in each region.

Material S1: The appendices.

Material S2: The simulation computer program to obtain the numerical solutions of genotypic and phenotypic frequencies of zygotes and the genotypic frequencies of gametes. The program can be run on Windows platforms and requires the .Net Framework V3.5 runtime library.

Material S3: The C++ source code of the genotypic and phenotypic frequencies of polysomic inheritance under double-reduction. The prefix of functions is GFZ (genotypic frequencies of zygotes), GFG (genotypic frequencies of gametes), PFZ (phenotypic frequencies of zygotes), or PFG (phenotypic frequencies of gametes). An example that is the function in the second case (i.e. G = AAAB) in Equation (A4) is given by

double GFZ4_iiij(double a1, double pi, double pj)

{

double pi2=pi*pi;

return (8*(-1+a1)*pi2*(-3*a1+2*(-1+a1)*pi)*pj)/pow(2+a1,2);

}

The synthesis of (4S-phenylpyrrolidin-2R-yl)methanol and 2S-methyl-4S-phenylpyrrolidine has been achieved via the double reduction of their cyclic sulfonamide precursors which themselves were prepared following the stereoselective intramolecular Heck reaction of a chiral pool derived 2,5-dihydropyrrole. We have recently described a process whereby cyclic aryl sulfonamides, such as 2, are reductively ring-opened to furnish amino products in which the aryl group is incorporated in the final compound. (Evans, P.; McCabe, T.; Morgan, B. S.; Reau, S. Org. Lett. 2005, 7, 43.) The precursors for this reaction were assembled using an intramolecular Heck reaction followed by reduction of the alkene. Overall, this sequence represents an efficient means to construct molecules of this type in which the aryl sulfonyl moiety acts as both an N-protecting group and as an aryl donor. Use of Benkeser's stronger reducing conditions enables molecules such as 4 to be prepared in which both the sulfonamide functional group and the aromaticity of the aryl substituent have been destroyed.

The market size of the Gear Reducer Consumption Market is categorized based on Application (Cars, Commercial vehicles, Agricultural, Industrial construction, Plant engineering) and Product (Single Reduction Gear, Double Reduction Gear) and geographical regions (North America, Europe, Asia-Pacific, South America, and Middle-East and Africa).

This report provides insights into the market size and forecasts the value of the market, expressed in USD million, across these defined segments.

The global truck differential market size was valued at USD 4,644.3 million in 2025 and is projected to reach USD 7,254.0 million by 2033, exhibiting a CAGR of 5.3% during the forecast period. The market growth is primarily driven by the increasing demand for trucks in various industries, such as construction, mining, and logistics. Furthermore, the rising adoption of electric vehicles is expected to fuel the demand for differentials designed specifically for electric trucks. The market is segmented based on application and type. By application, the market is divided into on-highway and off-highway. The on-highway segment accounted for the largest market share in 2025. However, the off-highway segment is expected to register a higher CAGR during the forecast period. By type, the market is classified into single-reduction, double-reduction, and triple-reduction differentials. The single-reduction differential segment dominated the market in 2025. However, the double-reduction differential segment is projected to grow at a significant rate during the forecast period.

Spur Gear Reducer Market Outlook

The global spur gear reducer market size was valued at approximately USD 3.5 billion in 2023 and is projected to reach USD 5.6 billion by 2032, growing at a CAGR of 5.2% during the forecast period. This growth is primarily driven by the increasing demand for efficient power transmission solutions across various industries. The surge in industrial automation and the growing need for highly precise and power-efficient gear systems in manufacturing units have acted as significant growth factors. Additionally, the enhancement of gear reducer technology catering to high torque and speed applications in various sectors fosters market expansion. The automotive industry's transition towards more fuel-efficient vehicles also significantly contributes to market growth, as spur gear reducers are integral in optimizing engine performance and efficiency.

One of the primary growth factors in the spur gear reducer market is the ongoing technological advancements in gear manufacturing processes. The integration of computer-aided design (CAD) and computer-aided manufacturing (CAM) technologies in gear production has significantly improved the precision and efficiency of spur gear reducers. Furthermore, the development of advanced materials and coatings that enhance the durability and performance of gear systems has broadened their application range, especially in high-performance sectors like aerospace and defense. These advancements have led to a reduction in operational downtimes and maintenance costs, consequently boosting their adoption in various industries.

The rising adoption of automation in industrial applications is another crucial driver for the spur gear reducer market. As industries strive to increase operational efficiency and reduce labor costs, the demand for automated machinery and robotics has surged. Spur gear reducers play a critical role in ensuring the smooth operation of such automated systems, as they provide the necessary torque and speed control. This trend is particularly evident in sectors such as automotive manufacturing and industrial machinery, where precision and efficiency are paramount. Additionally, the move towards Industry 4.0 is expected to further propel the demand for advanced gear reducers that can support smart and interconnected manufacturing processes.

The global emphasis on energy efficiency and sustainability is also contributing to the growth of the spur gear reducer market. Industries are increasingly focusing on reducing their carbon footprint, which has led to a greater demand for energy-efficient machinery and components. Spur gear reducers, known for their efficiency in power transmission, are being increasingly adopted in applications where energy conservation is a priority. This trend is expected to continue as more industries adopt green technologies and sustainable practices, thereby creating a favorable environment for the growth of the spur gear reducer market.

Bevel Gear Reducers are increasingly gaining traction in various industries due to their ability to handle high torque and provide smooth operation. These reducers are particularly favored in applications where space constraints are a concern, as their angular design allows for more compact machinery layouts. The unique geometry of bevel gears enables them to transmit power between non-parallel shafts, which is a significant advantage in complex machinery setups. As industries continue to innovate and seek more efficient power transmission solutions, the demand for bevel gear reducers is expected to rise. Their versatility and efficiency make them an attractive option for manufacturers looking to optimize performance and reduce operational costs.

Product Type Analysis

The spur gear reducer market is segmented by product type into single reduction, double reduction, and triple reduction gear reducers. Single reduction gear reducers are characterized by their simplicity and cost-effectiveness, making them suitable for applications requiring moderate speed reduction and torque. These reducers are widely utilized in automotive and simple industrial machinery applications where the demand for high-precision torque is not the primary concern. The simplicity of design and ease of maintenance also enhance their appeal, especially in cost-sensitive markets. As industries continue to focus on cost optimization, the demand for single reduction gear reducers is expected to remain steady.

Double reduction gear reducers

Carbon dioxide electrochemical reduction (CO2ER) has attracted considerable attention as a technology to recycle CO2 into raw materials for chemicals using renewable energies. We recently found that Zn-Al layered double hydroxides (Zn-Al LDH) have the CO-forming CO2ER activity. However, the activity was only evaluated by using the liquid-phase CO2ER. In this study, Ni-Al and Ni-Fe LDHs as well as Zn-Al LDH were synthesized using a facile coprecipitation process and the gas-phase CO2ER with the LDH-loaded gas-diffusion electrode (GDE) was examined. The products were characterized by XRD, STEM-EDX, BF-TEM and ATR-IR spectroscopy. In the ATR-IR results, the interaction of CO2 with Zn-Al LDH showed a different carbonates evolution with respect to other LDHs, suggesting a different electrocatalytic activity. The LDH-loaded GDE was prepared by simple drop-casting of a catalyst ink onto carbon paper. For gas-phase CO2ER, only Zn-Al LDH exhibited the CO2ER activity for carbon monoxide (CO) formation. By using different potassium salt electrolytes affording neutral to strongly basic conditions, such as KCl, KHCO3 and KOH, the gas-phase CO2ER with Zn-Al LDH-loaded GDE showed 1.3 to 2.1 times higher partial current density for CO formation than the liquid-phase CO2ER.

The parallel drive axle market is experiencing robust growth, driven by the escalating demand for passenger and commercial vehicles globally. The increasing adoption of electric and hybrid vehicles, coupled with stricter emission regulations, is further propelling market expansion. Technological advancements in axle design, focusing on enhanced fuel efficiency and durability, are key contributing factors. While the precise market size in 2025 is unavailable, considering a typical CAGR of 5-7% (a reasonable estimate for this sector given automotive market growth trends) and a hypothetical 2019 market size of $15 billion USD, a 2025 market value of approximately $20 billion USD is plausible. This growth is unevenly distributed geographically, with Asia-Pacific (particularly China and India) leading due to rapid industrialization and burgeoning vehicle production. North America and Europe also represent significant markets, though potentially exhibiting slower growth rates compared to the Asia-Pacific region. The segment breakdown reveals a strong preference for single reduction parallel drive axles, owing to their cost-effectiveness and suitability for many applications. However, the double reduction parallel drive axle segment is poised for substantial growth, driven by its superior load-bearing capacity and efficiency advantages in heavy-duty vehicles. Competition within the parallel drive axle market is intense, with numerous established players and emerging companies vying for market share. Key players such as Dana Incorporated, ZF Friedrichshafen AG, and Schaeffler AG are leveraging their technological expertise and global reach to maintain their dominance. However, several Chinese manufacturers are rapidly gaining traction, particularly in the electric vehicle segment, challenging the established players and potentially disrupting the market dynamics. Restraining factors include fluctuating raw material prices, stringent quality standards, and regional economic fluctuations. Future growth hinges on continuous innovation in axle technology, particularly in areas such as lightweight materials, advanced control systems, and integration with autonomous driving technologies. The market's trajectory will also be significantly shaped by government policies promoting sustainable transportation and the ongoing shift towards electric and hybrid vehicles.

The size and share of the market is categorized based on Type (Single Reduction Tandem Axle, Double Reduction Tandem Axle) and Application (Passenger Vehicles, Commercial Vehicles) and geographical regions (North America, Europe, Asia-Pacific, South America, and Middle-East and Africa).

Worm Gear Speed Reducer Market Outlook

As of 2023, the global worm gear speed reducer market size is valued at approximately USD 5.6 billion and is projected to reach USD 8.2 billion by 2032, demonstrating a compound annual growth rate (CAGR) of 4.5% over the forecast period. The steady growth of this market is fueled by the increasing demand for efficient power transmission systems across various industries. Factors such as technological advancements, the proliferation of automation in manufacturing, and the growing emphasis on energy efficiency and sustainability are pivotal in driving the market expansion. Worm gear speed reducers are essential in providing robust torque output and speed reduction in compact designs, making them indispensable in a range of applications.

The market growth is notably driven by the widespread adoption of automation in industrial applications. Industries are increasingly automating their processes to enhance productivity and efficiency, which has led to a heightened demand for reliable and efficient transmission systems like worm gear speed reducers. This trend is further bolstered by advancements in technology, such as the integration of IoT and AI into manufacturing processes, which require highly efficient and adaptable gear systems. The need for precision and reliability in these automated systems has positioned worm gear speed reducers as a vital component in various machinery, thus boosting their market demand.

Another significant growth factor is the rising focus on energy efficiency and sustainability within industries. Worm gear speed reducers are known for their high efficiency and ability to minimize energy loss, making them a preferred choice for eco-friendly applications. As industries strive to reduce their carbon footprint and adhere to stringent environmental regulations, the demand for energy-efficient components like worm gear speed reducers is increasing. Moreover, the trend toward renewable energy sources also contributes to market growth, as these gear reducers play a critical role in the operation of wind turbines and solar panel tracking systems.

Additionally, the burgeoning construction and automotive sectors are contributing to the market's expansion. In the construction industry, worm gear speed reducers are utilized in various equipment and machinery, such as cranes and conveyor systems, which are integral to building and infrastructure projects. The automotive industry's pursuit of advanced transmission systems to enhance vehicle performance and fuel efficiency also drives the demand for worm gear speed reducers. This is particularly pertinent as the global automotive industry shifts towards electric and hybrid vehicles, which require precise and compact gear systems.

Regionally, the Asia Pacific is anticipated to exhibit the highest growth rate over the forecast period. This region's growth is underpinned by rapid industrialization, urbanization, and infrastructural development, particularly in emerging economies like China and India. The presence of numerous manufacturing facilities and the expanding automotive industry further cement the region's dominant position in the market. North America and Europe are also significant markets, driven by technological advancements and a strong focus on energy-efficient solutions. In contrast, the Middle East & Africa and Latin America are expected to experience moderate growth, supported by ongoing industrialization efforts and infrastructure projects.

Product Type Analysis

The worm gear speed reducer market is categorized into different product types: single reduction, double reduction, and triple reduction. Each product type offers specific advantages that cater to diverse industrial needs. Single reduction worm gear speed reducers are widely used for applications that require moderate speed reduction and torque. They are favored for their simplicity and cost-effectiveness, making them suitable for standard machinery where space and budget constraints are critical considerations. This segment benefits from a broad range of applications, including conveyors, material handling systems, and basic industrial machinery.

Double reduction worm gear speed reducers, on the other hand, offer a higher degree of speed reduction and increased torque capacity. These are ideal for applications demanding more substantial torque and where more significant speed reduction is necessary. Industries such as automotive and aerospace, where precision and power are crucial, often rely on double reduction gear reducers. The capability of handling higher loads wh

The size and share of the market is categorized based on Type (Single Reduction, Double Reduction) and Application (Heavy Duty Trucks, Buses, Trailers) and geographical regions (North America, Europe, Asia-Pacific, South America, and Middle-East and Africa).

This is the data used to create the figures in the article:

Contrasting Views of the Electric Double Layer in Electrochemical CO₂ Reduction: Continuum Models vs Molecular Dynamics

DOI: 10.1021/acs.jpcc.4c03469

See the file "Naming conventions" for the file names and column/row meanings.

Aerofoils operating in a turbulent flow generate broadband noise by scattering vorticity into sound at the leading edge. Previous work has demonstrated the effectiveness by which serrations, or undulations, introduced onto the leading edge, can substantially reduce broadband leading edge noise. All of this work has focused on sinusoidal (single-wavelength) leading edge serration profiles. % In this paper, a new leading edge serration geometry is proposed which provides significantly greater noise reductions compared to the maximum noise reductions achievable by single-wavelength serrations of the same amplitude. This is achieved through destructive interference between different parts of the aerofoil leading edge, and therefore involves a fundamentally different noise reduction mechanism from conventional single-wavelength serrations. % The new leading edge serration profiles simply comprise the superposition of two single-wavelength components of different wavelength, amplitude and phase with the objective of forming two roots that are sufficiently close together and separated in the streamwise direction. Compact sources located at these root locations then interfere leading to less efficient radiation than single-wavelength geometries. A detailed parametric study is performed experimentally to investigate the sensitivity of the noise reductions to the profile geometry. A simple model is proposed to explain the noise reduction mechanism for these double wavelength serration profiles and shown to be in close agreement with the measured noise reduction spectra. The study is primarily performed on flat plates in an idealized turbulent flow. The paper concludes by introducing the double-wavelength serration on a 10\% thick aerofoil, where near-identical noise reductions are obtained compared to the flat plate.

Tetraiodotetraazapentacene I4TAP , the last missing derivative in the series of halogenated silylated tetraazapentacenes, was synthesized via condensation chemistry from a TIPS-ethynylated diaminobenzothiadiazol in three steps. Single and double reduction furnished its air-stable monoanion and relatively air-stable dianion, both of which were characterized by crystallography. All three species are structurally and spectroscopically compared to non-halogenated TAP and Br4TAP. I4TAP is an n-channel material in thin-film transistors with average electron mobilities exceeding 1 cm2(Vs)-1 .