Compressor Noise Research Articles

Investigation on improving the multi-operating condition performance of a rotary compressor based on variable stiffness valve

Improving valve design is crucial for enhancing the performance of rolling piston type rotary compressor. A novel variable stiffness valve based on PEEK and stainless steel was proposed. The stress-strain behavior of the novel valve was studied, and its operational characteristics, including opening and closing angles and over-compression losses, were analyzed in a compressor. It is shown that opening and closing angle of the new-designed valve were advanced compared to that of the original cylinder by about 2∼3°, leading to a general reduction in over-compression losses, with a maximum decrease of 4.15 W. The impacts of new-designed valve on compressor performance were experimentally investigated. The cooling capacity and coefficient of performance of compressors equipped with new-designed compared to original valve were improved by 1.1–1.7 % and 1.1–2.6 %, respectively. In addition, the input electrical power required for the new valve was observed to be 0.9–1.3 % lower. The incorporation of high-damping material in the new valve design significantly reduced compressor noise by 3–5 dB at the critical frequency bands of 630–1250 Hz. These findings offer valuable insights for enhancing the energy efficiency and noise reduction in rolling piston type rotary compressors.

Noise Analysis and Structural Optimization of Automobile Scroll Compressor Air Valve

The air conditioning compressor is a critical component in automobile heating, ventilation and air conditioning systems. However, compressor noise has long been a problem for automobile manufacturers. In recent years, the development and application of automobile air conditioning scroll compressors has increased significantly due to their low mechanical vibration and noise. However, their limitations in terms of airflow pulse and noise cannot be ignored, especially in low speed and high load conditions where the noise generated has a negative impact on driving and passenger experience. Noise and airflow pulses are important considerations that cannot be ignored. This study innovatively modifies the end cap structure of the scroll compressor, using the principles of expansion muffler and insertion tube structure, with the aim of improving the acoustic quality of the scroll compressor. The results show that the novel valve construction can significantly reduce the sound pressure level of the scroll compressor noise to a maximum of 75.20 dBA. The results of this study provide a theoretical basis and practical technical applications for future research and development in the automobile industry.

An Investigation of the Acoustic Enclosure of an Air Conditioning Compressor Using Response Surface Analysis and Topological Rigidity Optimization

A novel split-type air conditioning system is introduced to balance usability and portability. Unlike conventional split-type systems, where the compressor is typically placed outside, this system situates the compressor within the indoor unit, which may expose users to compressor noise. There are prominent peaks in the compressor noise spectrum, particularly at the compressor operating frequency and its harmonics, notably the second and third harmonics. The research presents a multilayered acoustic enclosure specifically designed for air conditioning compressors to address this issue without modifying the compressor or indoor unit casing. In order to get better sound insulation performance, a response surface methodology (RSM) is applied to optimize the thickness ratio, open area ratio, and open area height of the acoustic enclosure with predefined thickness. In addition, topological optimization is employed to strengthen weak areas of the acoustic enclosure. Then, experimental trials using the proposed acoustic enclosure are conducted in a semianechoic chamber. Results demonstrate significant reductions in noise levels, including 7.99 dB(A), 5.69 dB(A), and 5.19 dB(A) reductions in the fundamental frequency, second harmonic, and third harmonic noise of the compressor’s operating frequency, respectively.

FPGA Design and Implementation of Improved DFxLMS Algorithm for Compressor Noise Cancellation System

FPGA Design and Implementation of Improved DFxLMS Algorithm for Compressor Noise Cancellation System

Sensitivity of compressor aerodynamic noise prediction to time setup of CFD simulations using hybrid CAA method

This paper numerically studies the aerodynamic noise of a centrifugal compressor in a vehicle engine turbocharger. The hybrid CAA approach based on computational fluid dynamics (CFD) and acoustic boundary element method (BEM) in the prediction of aerodynamic noise is validated. The impacts of the time setup of unsteady CFD simulations on the prediction of compressor flow and aerodynamic noise are discussed. The results show that a large time step would result in unreliable numerical results, in which severe reverse flow and flow separation can be observed. The middle time step 2 deg. can get accurately predicted results while reducing the computational efforts. It is also found that a large total simulation time with a reasonable time step is helpful to improve predicted noise spectra. Moreover, the overall sound pressure level discrepancy of aerodynamic noise between numerical prediction and experimental measurement is less than 0.5 dB.

Analysis of interference of electromagnetic noise in an electric compressor for vehicle air‐conditioning systems with an integrated mechanical and electrical structure

AbstractSince a motor drive system contains an inverter (high‐voltage circuit) and gate drive circuits (low‐voltage circit) with a switching regulator, electromagnetic noise is generated in each of these two circuits, and noise interference between these circuits can occur. This paper discusses noise interference between the high‐ and low‐voltage circuits of an electric compressor system with an integrated mechanical and electrical structure. Analysis using LTspice shows that the experimental and analytical results are in good agreement when a very small stray capacitance occurs between the high‐ and low‐voltage circuits. An experiment using an actual compressor showed that conducted noise above 20 MHz can be reduced by up to 10 dB by reducing the effect of stray capacitance between these circuits.

Study of noise and structural characteristics of twin-screw air compressor based on multi-physical field coupling

For the problems of high noise and low efficiency of twin-screw air compressor, the mutual coupling effect of noise and structure for the twin-screw air compressor is studied by using acoustic-solid coupling technology. The simulation model of acoustic-structural coupling of twin-screw air compressor is established. Combining acoustic wave theory calculation with structural characteristics, the sound pressure level distribution and structural deformation law of different tangent planes of the shell at different frequencies under external excitation are studied. The results show that when the frequency is different, the more intensive the acceleration distribution on the shell surface is, the greater the sound pressure level is. At the same frequency, as the incident pressure wave increases, the deformation on the shell also increases, and the maximum shell deformation and the maximum sound pressure level both appear around 2000 Hz. As the frequency increases, the acceleration distribution on the surface of the shell becomes more denser and the sound pressure level becomes larger.

Active electric machine control to reduce compressor noise in heat pumps

As heat pumps help to reduce CO2 emission in residential heating, rapidly growing heat pump sales are predicted. In order to install heat pumps in densely populated residential areas, they must comply with strict noise requirements. Due to advances in control technology in recent years, it seemed promising to investigate the noise reduction potential of a heat pump by means of optimized control. An active control strategy called Current Shaping (CS) has been applied to reduce compressor induced heat pump noise by applying suitable currents to the compressors electric machine. For this purpose, by CS we superimposed suitable current harmonics on the almost constant Iq driving current. In this article we focus on how these modified driving currents affect the noise emitted from the compressor and how this reduces heat pump noise. A compressor test bench was built to perform the CS optimization procedure and to determine noise optimal currents by minimizing compressor vibration. An important finding of this investigation is that the compressor vibrations can be efficiently reduced by CS, and hence also the noise emissions. The vibration reduction potential depends on the compressor harmonic and the operating condition. Additionally, pressure pulsations were measured within the refrigerant pipes and found not to be affected by CS. After the test bench optimization, we applied the optimized currents to a heat pump in a sound chamber to proof that these optimized currents efficiently reduce heat pump noise. For the investigated frequency range of up to 400 Hz our investigations show the three following: First, active electric machine control CS is a suitable method to reduce heat pump noise. Second, the test bench, presented in this paper is suitable to determine the CS current harmonics to reduce heat pump noise. Third, it can be confirmed that the main heat pump noise source is compressor vibration. In general, the two main noise sources of a heat pump are the fan and the compressor. For the compressor there are three noise paths, namely structure-borne and air-borne noise, both excited by compressor vibration, and fluid-borne noise, excited by pressure pulsations in the refrigerant in the piping system. Therefore, from the investigations presented here, it can be derived that the compressor noise is dominating heat pump noise. Moreover, compressor vibrations are dominating heat pump noise and not pressure pulsations in the piping system.

Research on vibration and noise characteristics of scroll compressor with condenser blockage fault based on signal demodulation

The scroll compressor is the core component of the air conditioning system. It is important to accurately evaluate the operation status of the air conditioning system. In this paper, the condenser failure is simulated to explore the impact on the scroll compressor by building an air conditioning system experimental platform. The characteristic frequencies and generation mechanisms of vibration and noise signals are discussed through Time-frequency analysis. The characteristic frequencies in the x, y, and z directions are shaft frequency, second harmonic frequency of stator slot and magnet frequency. Abnormal vibration of the scroll compressor caused by changes in pressure and unbalanced electromagnetic force. The modulation characteristic frequency of the signal and the trend of modulation characteristic changes under fault conditions are discussed through signal demodulation methods. The amplitude modulation of the characteristic frequency is enhanced by the unbalanced electromagnetic force on the shaft rotor. The amplitude of the modulation characteristic frequency of the vibration signal in the three directions and the noise signal increases by 45.0%, 17.3%, 71.4% and 123.0%. This study reveals the mechanism and modulation characteristics of vibration and noise of the scroll compressor, and provides support for its fault diagnosis and status recognition.

Gradient Pore Structured Elastic Ceramic Nanofiber Aerogels with Cellulose Nanonets for Noise Absorption

AbstractThe expeditious growth of modern transportation and industrialization has given rise to serious noise pollution, which has brought disaster to the world economy and human health. Most existing sound‐absorber with single pore structures suffer from large weight and the incidence and dissipation of noise that are difficult to be enhanced simultaneously. Herein, gradient‐structured elastic ceramic nanofiber aerogels with cellulose nano‐nets are successfully structured through step‐by‐step directional freeze‐casting technology, which has a gradient structure of “larger pore‐middle pore‐smaller pore” in the propagation direction of sound waves and dual nanofiber networks perpendicular to the direction of sound waves. The integration of gradient pore structures and dual nanofiber networks effectively improves the acoustic contact area of aerogels while increasing the acoustic incidence. The noise reduction coefficient of the obtained lightweight gradient aerogels (average density only 9 mg cm−3) reaches 0.58, and the low‐frequency air compressor noise can be reduced by 23.1 dB. Besides, the silica sol with hydrophobic groups endows gradient aerogels with good mechanics (plastic deformation only 5.7% after 1000 compressions) and superhydrophobic properties (water contact angle of ≈150°). The successful construction of gradient‐structured dual network nanofiber aerogels will offer new horizons for the upgrading of nextgen noise absorbers.

Development of flow-vibroacoustic coupled numerical methods for prediction of noise radiation due to flow-born vibration of compressor discharge piping system

The compressor and fan in air conditioner outdoor unit are the core component which deter-mines noise performance as well as cooling or heating performance. Among these, the com-pressor has larger contribution to the noise of outdoor units. For high efficiency air condition-er, the size and operating speed of compressor are smaller and faster. The high-speed com-pressor causes loud noise which is complaints for the customer. Traditionally, it is well-known that the vibration of compressor and connected duct is main noise source. However, as the compressor speed increases, the refrigerant flow in the compressor discharge duct also emerged as a major noise source. To reduce the compressor noise operating at high speed, it is necessary to analyze vibrational and acoustic characteristics of compressor discharge duct. This duct noise has the two-types source: structure born noise and flow induced noise. The structure born noise is generated by the duct vibration caused by compressor movement. For the flow induced noise, the static pressure field of refrigerant flow in the duct is vibrational source. In this paper, the compressor discharge duct noise considering two mechanisms was investigated. The refrigerant flow is solved using CFD and duct vibration and noise radiation are computed by FE-BE method.

Effect of differential tip clearance on the performance and noise of an axial compressor

Rotor tip clearance (TC) shows significant effects on the stability and performance of aero-engine compressors. TC is also related to the producing of noise and tip leakage flow which is an indicator of critical operating conditions for rotating stall or surge. In this paper, the effect of TC on stall evolution process under different TC values is studied on a single-stage compressor with low speed and high load, and a frequency-domain interferometer diastimeter for high-resolution measurements is applied to accurately measure the TC value. In the present study, a soft-wall casing made of grindable material is applied to achieve the “zero clearance” condition, and casings with different diameters are adopted to reach different clearance values. Experimental results show that pressure rise and efficiency are improved with a small TC. With the TC varying from zero to a certain large scale, experimental results have proved that there is an optimal TC with the presence of maximum flow margin. In addition, eighty measurement points are evenly distributed around the casing circumferentially at the leading edge of the blade to analyze the circumferential flow characteristics of the tip flow field. And twenty wall-flush mounted microphones are evenly distributed circumferentially to monitor the induct sound field of the compressor, and the experimental results show that the sound pressure level (SPL) of the compressor is lowest at a relatively small TC rather than zero. The influence of different TC values on compressor is discussed based on the analysis of the pressure fields, stall process, and the acoustic signal. Furthermore, a detailed discussion of rotating instability (RI) brought about by large clearances is provided.

Use of CFD to optimize the design of a shunt pulsation trap (SPT) used for noise and vibration mitigation in oil free screw compressors

Noise and vibration are problems that are inherent in screw compressors and other Positive Displacement (PD)Machines. This problem is driven partly by the lobe passing frequencies inside these machines that are generated due to the meshing between the gate and main rotors teeth. Because these compressors are operated over a wide speed range and at various loads they usually run at off-design conditions leading to either over or under-compression. In both scenarios, the pressure within the compressor always changes rapidly to match the discharge or process pressure when the discharge opens thus leading to pulsation and noise. To ensure that the compressor is operated without over and or under compression, which also negatively affects the compressor efficiency Hi-Bar Blowers, Inc developed a Shunt Pulsation Trap (SPT) that will contain and reduce the pulsation inside the compressor cavities thus eliminating the use of a silencer at the inlet and the discharge. During the SPT development the CVS Silo King (SKL 1100) compressor was selected for benchmarking this technology. CFD was used extensively to simulate the SKL 1100 without and with the SPT integrated, which allowed the SPT design to be optimized. This paper will present the results obtained to demonstrate that this technology has the potential to eliminate over and under compression while at the same time leading to energy savings and reducing the compressor footprint and the noise and vibration that are commonplace in screw compressors.

Mechanism of Axial Compressor Tip Clearance Noise Based on Taylor–Couette Flow Rotating Instability

Abstract Prediction of the tip clearance noise (TCN) of axial compressors is essential to accurately determine the noise level of the compressor, because it is left unattenuated during propagation. The existing studies on numerical methods are inadequate for accurate determination of the TCN owing to the limited understanding of the physical phenomenon. The most convincing explanation is that the TCN is generated because of the instability in shear waves in the tip clearance region. In this study, the rotating instability theory was developed further by modeling the physical phenomenon of the instability as a Taylor–Couette (T–C) flow. The TCN sources were obtained using T–C flow modeling, and duct noise analysis was performed to obtain the TCN at various locations and frequencies. The TCN predictions were compared with the existing experimental results and noise results obtained using FW–H. Results showed that the T–C flow modeling is sufficiently accurate for predicting the frequencies, wavenumber distributions, and SPL of the tip clearance noise of axial compressors.

Study on Characteristics and Control of Aerodynamic Noise of a High-Speed Centrifugal Air Compressor for Vehicle Fuel Cells

As the main noise source in the hydrogen fuel cell system, the noise level of the centrifugal air compressor greatly affects the comfort of the hydrogen fuel cell vehicle. For reducing the noise level of centrifugal air compressors, the noise characteristics and control of a high-speed two-stage compressor prototype are studied in this paper. Firstly, the near-field noise measurement, along with the independent component analysis, is carried out to identify the noise source of the developed compressor. Results showed that the “buzz-saw” noise at the rotating fundamental frequency and its low order harmonic frequency in the aerodynamic noise is prominent in the noise spectrum. Thus, the aerodynamic noise characteristics are predicted and analyzed using the CFD–BEM coupling aeroacoustic calculation model. Based on the analysis results, a noise control method coupling the structure optimization and perforated muffler is proposed. The results show that the sound pressure level of the air compressor at 1 m away from the surface is reduced by 4.1 dBA after the structural optimization. A perforated muffler applied in the pipe system of the air compressor can accomplish a reduction of 5.8 dBA in the sound pressure level of the air compressor by impeding the noise transmission on the path. With the coupled noise control methods above, the sound pressure level of the air compressor is reduced from 78.8 dBA to 68.9 dBA under the rated condition.

Gas compressor noise does not influence tree swallow nestling condition or immune response

AbstractAnthropogenic noise pollution, such as that derived from traffic and industrial machinery, has been identified as an urgent conservation priority as it is often louder and more prevalent than natural acoustic stimuli, and can act as a stressor on wildlife. Research in avian systems has shown that anthropogenic noise can affect physiology and reproductive success of adult birds – but effects on juvenile birds have been less‐studied despite their being potentially more vulnerable during the nestling period. What studies have been done have shown remarkable variability in juvenile response to anthropogenic noise, suggesting that effects are highly context‐ and species‐specific. Here, we investigate the effects of gas compressor noise, an increasingly prevalent and biologically relevant noise stressor produced during natural gas production, on juvenile tree swallows (Tachycineta bicolor). Gas compressors generate considerable sound pressure as they work to pressurize gas pipelines for downstream distribution. We predicted that exposure to increased noise during incubation and the nestling period would result in smaller chicks in poorer body condition and with a dampened immune response. Surprisingly, we found no evidence for any of these predictions, providing further evidence that noise effects on juvenile birds is highly variable, and we explore ways in which individual birds may compensate for the effects of disturbance at the nest.

Prediction and experimental study of radiated noise of rotating vane compressor under compound effects of multiple sources excitations

Aiming at the problem that it is difficult to accurately predict the radiated noise of rotary vane compressor under multi-source excitation, in this paper, the rigid body dynamics model and the dynamics model of airflow pulse excitation of the suction-compression-exhaust process of the rotary vane compressor were established, and the mechanism of multi-body contact excitation and airflow pulsation excitation for rotating vane compressor is expounded. Meanwhile, a flexible multibody finite element mesh model including a rotor, blades, cylinder, end cover and shell was established, and mechanical excitation and airflow pulse excitation were taken as mechanical boundary conditions to calculate the vibration response characteristics of the rotary vane compressor. To estimate the radiated noise of the rotary vane compressor, a compressor acoustic boundary element model was established, and a noise test bench system was built in a semi-anechoic chamber to compare and analyze the calculated noise value. At constant speed and acceleration, the rear sound pressure value is larger, followed by the right part, which is close to the exhaust port, and the front sound pressure is obviously lower than other points. The maximum relative error of sound pressure levels at four field points is 4.8%, and the average relative error of all measured points is 2.4%. The measured values are in good agreement with the calculated values, which verifies the accuracy of the radiated noise prediction model of rotary vane compressor.

Applying the phononic crystal concept to the intake muffler of a refrigeration compressor

Many previous works explore the creation of wave stop bands (bandgaps) using periodic structures. Aiming at improving the transmission loss of a muffler used in a refrigerant compressor, this work proposes the redesign of an existing intake muffler using the concept of wave attenuation bands caused by Bragg scattering. The challenge consists in designing a phononic crystal (PnC) with bandgaps in the audio frequency range with the size constraints of a practical muffler application. The first part of the research focuses on the development and validation of numerical and experimental techniques to provide guidelines for periodic muffler design. The second part consists in applying the developed concepts and tools to a real compressor muffler following the constraints of the product specifications. A shape optimization technique is used to enlarge the bandgap while keeping the unit cell length in the order of tens of millimeters. Two designs were 3D-printed and tested on the real compressor, reaching 7 dB reduction on the sound power level (SPL) in the aimed frequency band and 4 dB reduction on the overall compressor noise level.

Simulation and experimental research on aerodynamic noise of gas turbine 1.5-stage axial compressor

The aerodynamic noise of the axial compressor is one of the significant noise sources of gas turbines, and it has gradually attracted the attention of the majority of researchers. In this paper, the aerodynamic noise characteristics of a 1.5-stage axial compressor were studied through simulations and experiments. A full-channel calculation of a three-dimensional unsteady flow field was computed using the Reynolds-averaged Navier Stokes (RANS) method. Spectral analysis of the static pressure in the tip clearance area was in good agreement with experimental data, which verifies the accuracy of the calculations. The volume and surface sound sources were extracted from computational fluid dynamics calculations to estimate the far-field acoustic characteristics of the compressor. The simulated results of the sound field were verified by a comparison with experimental data. The results show that the sound source intensity of the compressor’s guide vanes is much lower than that originating in the rotor and stator, which indicates that the interaction between the rotor and stator is much stronger than that of the guide vane and rotor. This conclusion is consistent with the unsteady flow field analysis. To investigate the influence of complex geometric structures on sound propagation, three sets of finite element grids were employed for noise prediction. The calculations considering all structures are in the best agreement with the experimental data, which shows that complex structures cannot be ignored when calculating aeroacoustic predictions.

Silencer for high-frequency turbocharger compressor noise via an acoustic straightener

Decades of successful research and development on automotive silencers for engine breathing systems have brought about significant reductions in emitted engine noise. A majority of this research has pursued airborne noise at relatively low frequencies, which typically involves planar wave propagation. However, with the increasing demand for downsized turbocharged engines in passenger cars, high-frequency compressor noise has become a challenge in engine induction systems. Elevated frequencies promote multi-dimensional wave propagation rendering at times conventional silencer treatments ineffective due to the underlying assumption of one-dimensional wave propagation in their design. The present work focuses on developing a high-frequency silencer that targets tonal noise at the blade-pass frequency within the compressor inlet duct for a wide range of rotational speeds. The approach features a novel "acoustic straightener" that creates exclusive planar wave propagation near the silencing elements. An analytical treatment is combined with three-dimensional (3D) acoustic finite element method to guide the early design process. The effects of mean flow and nonlinearities on acoustics are captured by 3D computational fluid dynamics (CFD) simulations which are then utilized to introduce geometry modifications that reduce flow losses and suppress noise generation due to flow-acoustic coupling. The effectiveness of the silencer in the presence of mean flow is demonstrated by computing the transmission loss across the configuration from 3D CFD predictions.