Browse Topic: Compressors
The increasing electrification of vehicles means that heating, ventilation and air conditioning systems have a broader range of tasks and a different priority assessment. In electric cars, air conditioning systems are not only responsible for cooling the passenger compartment, but also for controlling the battery temperature, particularly during rapid charging, which represents a high-load operating point. Furthermore, achieving high thermodynamic efficiency is desirable, as this directly impacts the range of electric cars. The elimination of the combustion engine as a major source of noise prioritizes the noise, vibration and harshness behavior of the refrigerant compressor for product selection. To investigate the vibration and acoustic behavior, as well as the fluid dynamic forces resulting from the cyclic compression principle of an electric refrigerant compressor, a test rig was developed that allows compressors to be operated and measured in isolation in an anechoic chamber under various defined operating conditions. This test rig has been expanded in two ways within the scope of this work. Firstly, the compressor can be either rigidly attached to a dead mass using a VDA mount or measured while suspended freely. Secondly, a new R744-compatible refrigeration circuit has been added to the test rig, enabling compressors operating with the environmentally friendly refrigerant CO₂, which has so far only been used by a few manufacturers in selected models, to be tested. Measurement results obtained using this test rig provide valuable insight into the vibration behavior and sound spectra of the refrigerant compressor's fluid, structural, and airborne noise when operating at different points.
The interior noise and thermal performance of the passenger compartment are critical criteria for ensuring driving comfort [1]. This paper presents the optimization of air conditioning (AC) compressor noise, specifically for the low-powered 1.0 L - ICE engine paired with a 120 cc IVDC compressor. This combination is quite challenging due to the high operational load & higher operating pressure. To enhance better in-cabin cooling efficiency, compressor’s operating efficiency must be improved, which necessitates a higher displacement of the compressor. However, increased displacement results in greater internal forces which leads to more structure-borne induced noise inside the cabin. For this specific configuration, the compressor operating pressure reached up to 25 bars under most driving conditions. During dynamic driving scenario, a metallic tonal noise from the compressor was reported in a compact vehicle segment. It is reported as very annoying to passengers inside. A comprehensive root cause analysis was conducted, including Transfer Path Analysis (TPA), evaluation of compressor fixation points stiffness, and dynamic noise signature analysis. The investigation revealed that the metallic noise was a combination of moaning and whining sounds, primarily caused by internal excitation forces within the compressor. These forces generated dominant excitations at high operating pressures, resulting in the observed tonal noise. Several countermeasures were explored, including changes to the compressor pulley ratio to decouple engine firing frequency excitations, modifications to the AC pipe bends to reduce excitation forces, and optimization of acoustic mass and compressor mounting stiffness. Collaboration work has been done with the supplier focused on fine-tuning the Mass Flow Control Valve (MFCV) settings [6] and adjusting compressor shaft tolerance. The most effective solutions were the compressor pulley ratio change and the modification of the compressor’s planetary plate angle, which together achieved an improvement of approximately 6 dB(A) in compressor order noise, significantly reducing customer-perceived annoyance. As a result, key NVH (Noise, Vibration, and Harshness) design rules have been established and implemented
The rapid rise in electric vehicle (EV) adoption demands innovative thermal management solutions to boost battery performance and passenger comfort. This paper introduces a novel control strategy for simultaneous battery and cabin cooling in EVs, utilizing a two-stage fuzzy logic controller. The proposed system incorporates a detailed plant model to simulate real-world conditions and dynamically optimize compressor speed, ensuring energy-efficient thermal management. In the first stage, the fuzzy controller sets the initial compressor speed based on primary inputs such as battery and cabin temperatures. The second stage fine-tunes this speed by considering secondary parameters like condenser and chiller pressures, along with the power output ratio from the plant model. This multi-stage approach guarantees efficient cooling for both the battery and cabin while maintaining safe operating conditions. Our research showcases the efficacy of this control strategy in achieving optimal thermal management in EVs, tackling the challenges of maintaining battery and cabin temperatures under varying ambient conditions. The findings suggest ways to improve energy efficiency and make components last longer, leading to more sustainable and reliable electric transport.
Compressor durability is a critical factor for ensuring the long-term reliability of Mobile Air Conditioning (MAC) systems in passenger vehicles. This study presents a software based strategy for enhancing compressor life using Smart Fully Automatic Temperature Control (FATC), requiring no additional hardware. The proposed approach leverages existing inputs from the FATC and Engine Management System (EMS) to intelligently manage compressor operation, with a focus on addressing challenges related to prolonged non-usage. In extended inactivity scenarios such as during cold weather, vehicle exportation, storage, or breakdowns, lubrication oil tends to settle in the compressor sump, leaving internal parts dry. Sudden reactivation at high engine speeds under such conditions can cause increased friction, wear and even compressor seizure. To mitigate this, an intelligent reactivation protocol has been developed and integrated into the Climate Control Module (CCM). This protocol continuously monitors parameters such as ambient and evaporator temperatures, solar load and engine RPM to detect extended inactivity. Upon detection, it initiates a controlled compressor activation sequence involving short duration clutch engagement cycles, allowing gradual lubrication and preventing mechanical stress. The strategy includes a multivariable detection framework and dynamic threshold adaptation that tailors activation logic to real-time environmental and operational conditions. A Smart transition mechanism ensures smooth switching between safe and regular operation modes. Preliminary testing shows that this method effectively minimizes dry starts, reduces mechanical wear and supports long term compressor health. The proposed strategy offers a cost effective and robust solution for improving compressor durability, lowering maintenance costs and enhancing user satisfaction.
This research addresses the issue of noise, vibration, and harshness (NVH) in electric buses, which can hinder their widespread adoption despite their environmental benefits. With the absence of traditional engines, NVH control in electric vehicles focuses on auxiliary components like the air compressor. In this study, the air compressor was identified as a major source of vibration, causing harsh contact between its oil sumps and mounting bracket. Analyzing the vibrations revealed that the sump and bracket were not moving freely, increasing noise. Modifying the bracket design to allow more movement between the components successfully reduced both noise and vibration. The paper details the experimental process, findings, and structural damping methods to mitigate NVH in electric buses.
This paper presents experimental research aimed at developing novel low lubrication methods for rotorcraft and jet engines, focusing on sustaining minimal lubrication to prevent catastrophic bearing failure during loss of lubrication (LoL) events or to increase fuel consumption performance on once-through, fuel-oil bearing lubrication engines. Utilizing two high-speed bearing test rigs simulating low and high thrust class engine conditions, the study establishes lower bounds for oil flow rates necessary to maintain thermal stability and prevent thermal runaway in hybrid ball bearings. These findings inform the design of the Zulu Pod (ZPod), a passively driven, self-contained oil delivery system that uses engine compressor bleed air to precisely meter lubricant flow. Engine test stand results demonstrate that replacing traditional fuel-oil lubrication with the ZPod system reduces thrust specific fuel consumption (TSFC) by an average of 7%, with up to 11% savings, without compromising engine thrust or bearing health. The ZPod offers a simplified, efficient alternative to fuel-lubricated systems by eliminating fuel diversion for lubrication, enhancing fuel efficiency, and maintaining bearing performance in attritable or single-use engines. Additionally, the study highlights the potential of minimal lubrication supplied by the ZPod to extend operational life during LoL scenarios, enabling safer aircraft recovery. Future work will focus on extending testing to higher thrust classes and optimizing ZPod designs for broader applications.
The International Space Station (ISS) is made livable in great part thanks to a system that captures and removes CO2 from the air. The workhorse inside that system is a compressor, which fulfills its CO2-capture duties, but at a cost: It is noisy and requires frequent maintenance. Engineers at NASA used modeling and simulation with experimental testing to analyze the next generation of compressor designs that get the job done more quietly, with fewer maintenance needs, and at lower fabrication cost.
With the advent of electric and hybrid drivetrain in the commercial vehicle industry, electrically driven reciprocating compressors have gained widespread prominence. This compressor provides compressed air for key vehicle systems such as brakes, suspension systems and other auxiliary applications. To be a market leader, such an E-compressor needs to meet a myriad of design requirements. This includes meeting the performance by supplying air at required pressure and flow rate, durability requirements and having a compact design while maintaining cost competitiveness. The reed valve in such a compressor is a vital component, whose design is critical to meet the aforementioned requirements. The reed valves design has several key parameters such as the stiffness, natural frequency, equivalent mass, and lift distance which must be optimized. This reed valve also needs to open and close rapidly in response to the compressor operating speed. Since it is the order of milliseconds, the valve is subjected to high velocity and impact force during this short time. A 1-D AMESim representation of the compressor has the reed valve modeled as an equivalent spring mass system. 3-D static structural analysis is performed using FEA tool to predict the stiffness, natural frequency and equivalent mass which acts as the input to the 1-D model. The overall performance of the compressor is then predicted through the 1-D Model simulation. The pressure data from this 1-D model is fed back to FEA to perform a 3-D transient dynamic analysis. The impact velocity and dynamic stresses induced during valve operation is studied to ensure reed valve durability. Optimization of the design parameters of reed valve is performed by synergistically combining the key insights from the AMESim performance outputs as well as the stiffness and dynamic stress prediction from FEA.
In automotive air conditioning systems, compressor is used to convert low pressure low temperature refrigerant into high pressure high temperature refrigerant. Various types of compressors like swash plate, rotary vane, scroll etc. are widely used in the automotive industry for air conditioning applications. In rotary vane compressors, thermal protector is used as a safety device, designed to prevent the compressor from overheating during refrigerant compression process. When the discharge temperature exceeds the preset limit of thermal protector, the thermal protector will activate and stop the electrical supply to compressor clutch to stop the compressor operation thereby preventing potential damage to air conditioning system, engine, and other nearby parts of the vehicle. This technical paper explores the various real-world scenarios for a hot country like India, which may result into higher discharge temperatures of compressor resulting into activation of thermal protector. The research encompasses vehicle level evaluations, replicating real world operating scenarios or misuse scenarios that may be evaluated for a vehicle with different load conditions of the air conditioning system and environmental conditions to consider the deletion of thermal protector from the system. The results of this analysis will be imperative in identifying the conditions that must be evaluated to justify the elimination of thermal protector in a particular compressor, assuring that the system's reliability and safety remains intact.
Customers expect more advanced features and comfort in electric vehicles. It is challenging for NVH engineers to reduce the vibration levels to a great extent in the vehicle without adding cost and weight. This paper focuses on reducing the tactile vibration in electric vehicle when AC is switched ON. Vibration levels were not acceptable and modulating in nature on the test vehicle. Electric compressor is used for cabin cooling and battery cooling in the vehicle. Compressor is connected to body with the help of isolators. Depending upon cooling load, the compressor operates between 1000 rpm and 8000 rpm. The 1st order vibration of compressor was dominant on tactile locations at all the compressor speeds. Vibration levels on steering wheel were improved by 10 dB on reducing the dynamic stiffness of isolators. To reduce the transfer of compressor vibration further, isolators are provided on HVAC line connection on body and mufflers are provided in suction and discharge line. With the above modifications, steering wheel vibration levels were reduced by ~ 2 dB. It is identified that radiator fan Pulse Width Modulation (PWM) frequency is also contributing to higher tactile vibration. Shifting PWM frequency to high frequency and stiffness increase on the fan motor casing has reduced the vibration levels by ~ 16 dB and cabin noise by ~ 2 dB (A). Alternative solutions like reducing of fan isolator stiffness is also explored. Blower vibrations contributing to steering wheel vibrations were reduced by controlling the unbalance on the blower. With all the modifications, tactile vibration levels are reduced considerably by ~ 20 dB. Modal criteria during design of compressor bushes and the NVH requirements during selection of fan PWM frequency to avoid higher levels of vibration during AC ON condition are explained.
The supplier is committed to all facets of the H2 economy as volume production of its power module kicks off for Nikola's Class 8 fuel-cell truck. At its oldest and largest location - a site long accustomed to manufacturing parts for combustion engines - Bosch is now producing what it calls the most complex system it has ever developed: a fuel-cell power module (FCPM). Production at the Stuttgart-Feuerbach site in Germany officially kicked off in July during a Bosch Tech Day event attended by global media. The pilot customer for the FCPMs is Nikola with its Tre hydrogen fuel-cell electric truck, which is expected to launch in North America in the third quarter of 2023. Bosch is committed to all facets of the hydrogen value chain, from developing an electrolysis stack and components for electrolyzers for H2 production, to engineering a drive solution for hydrogen compressors in filling stations. The supplier plans to invest nearly $2.6 billion between 2021 to 2026 in the development and manufacturing of hydrogen technologies - with nearly two-thirds of that amount devoted to the fuel-cell powertrain, Dr. Markus Heyn, chairman of the Mobility Solutions business sector, said during the Tech Day presentation.
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