A wide range of test benches dedicated to vehicle, powertrain, engine and associated components testing

Tests related to engines (combustion, micro-hybrid, hybrid, electric) of complete vehicles or their components (powertrain or other component) require different test bench technologies (inertia test bench, brake test bench, dynamic test bench) in different versions: roller test benches, PWT and e-PWT benches, engine test benches, engine component test benches, characterization benches...

A test bench is a set of equipment installed in a room generally tempered and ventilated.  It can be very simple in the case of elementary engine function tests, or very complex in the case of simulation of real operation of a PWT or a complete vehicle.

 

 

Our engineering department has a strong expertise in this field having already designed many benches for our internal needs (powertrain test bench, e-motor test bench, ElectroMagnetic Compatibility test bench, etc.) and to cover the needs of our customers.

 

 

 

Our services on test benches can have several objectives. It can be about tests :

• Development: fine-tuning (optimal adjustments to be made to the definitions made by the design offices), calibration of engine control systems, qualification of the performance of components or complete engines. This involves validating the technical solutions proposed and developed in terms of design, thermodynamics, material resistance and endurance.
• Approval or validation (normative aspect): verification that the vehicle meets pollution standards and specifications in terms of consumption and power.
• Validation and control (quality aspect): qualification of powertrain or organ endurance, accelerated ageing tests and/or reliability tests, specific endurance cycles...

 

 

 

Which test benches for which uses

The test benches for testing vehicles and their various components (complete powertrain or sub-assemblies) are almost as numerous as the parameters that need to be optimized for more efficient mobility.

 

 

The different types of services for tests on electric motors and e-PWT

Depending on whether the vehicles are hybrid, electric or even use a hydrogen fuel cell, different performance topologies are to be considered:

 

 

 

 

 

Climatic chassis dynometer / roller bench

Climatic engine test bench

Climatic engine test bench

• Iso-speed characterization
• Performance, Consumption, Emission / Pollution control
• Cold starting (HW definition / calibration)
• Spark plug fouling
• Vehicle cycles
• VHL cycles with simulated driving conditions
• Heat up
• Climatic validation

•     Running-in, full load curves
•     Cold starting
•     Friction losses study (with ancillary pumps)
•     Characterization
•     Heat up
•     Calibration (energy and component development)
•     Thermal validation of electric motor
•    Independent fluid control: air, water, oil, EGR, Water CAC

 

Dynamic calibration test bench

Durability engine bench - heavy duty applications

Durability engine test bench - Thermal shock

• Energy and component development
• Characterization of functions
• Durability cycles
• Running-in, Full load curves
• Knocks
• ODB

• Mechanical development
• Characterization of functions
• Gearbox ratio imposition on cycle
• Running-in, Full load curves
• Durability Cycles
• OBD

• Rapid variation of temperatures
• Characterization of functions
• Water and engine oil
• Durability cycles

 

 

 

 

Dynamometers: dynamic or stationary dynamometers?

A dynamometer is a device that allows the simultaneous measurement of the torque and rotational speed (rpm or tr/min) of a motor, engine or any other primary rotary engine, in order to calculate its instantaneous power, usually displayed by the dynamometer itself in the form of kW.
By recording a multitude of torque and power values at different speeds, a curve is derived that represents the overall performance of the motor.
In addition to being used to determine torque or power characteristics, dynos are used in standard emissions testing, but also to simulate the road load of the engine or the entire powertrain.

 

Beyond simple power and torque measurements, dynamometers can be used as part of a test stand for various engine development activities, such as calibration of engine management controllers, detailed combustion behavior studies, etc.
The use of a chassis dynamometer allows to get rid of many parameters influencing full-scale tests (human factor, driving conditions, weather...) and ensures the reproducibility of the tests. It is adapted to validate the consequences of adjustments and modifications.
In most cases, it is necessary to reproduce or simulate all the functions present on the engine in the real application (power steering, alternator, vacuum pump of the braking circuits, air conditioning...).
Thus, for an engine test bench, the engine is associated via a transmission with a load machine (controlled by the engine test bench control) simulating its environment.

 

The two main operating modes of test benches (braking only or braking and drive) define the two main categories to which they belong: stationary benches and dynamic benches capable of reproducing transients with or without energy generation.
These 2 operating modes correspond to a vehicle, in the acceleration phase (the engine is requested to deliver the power necessary for the vehicle to reach the required speed) and in the braking or engine drive phase (the inertia of the moving vehicle drives the organs and the thermal engine).

 

 

Dynamometers have often used eddy current brake type devices as load machines, the control of which imposed a relatively constant resistive torque on the motor under test. These devices are now often replaced by an electric machine which has the advantage of being more dynamic and can supply energy (not just consume it).

 

During the acquisition measurements, each combination of engine speed (rpm) and torque supplied corresponds to an engine operating point. Given the variations in the dynamic behavior of combustion, hybrid and electric engines according to their operating point, it is necessary to verify the ability of the engine control to ensure the required performance for all operating points of the engine field.

Similarly, it is important that the engine test bed is capable of switching quickly and correctly from one operating point to another. Engine test stands that are capable of fast switching between operating points are called high dynamic engine test stands.

Highly dynamic engine test beds can reproduce vehicle driving phenomena (acceleration, deceleration, gear change, etc.).

 

 

 

.A stationary test bench uses a brake to measure the characteristics of the motor. It is a question of measuring the resistance that the brake opposes to the engine. For a given engine speed, the dynamometer associated with the dyno's braking device can determine the corresponding applied force.

 

Different technologies of brake dynos exist: eddy current brake, hysteresis brake, powder brake... eddy current brake, hysteresis brake, powder brakes…

• Eddy current dynamometers (or EC for Eddy current also called Foucault's currents) are currently the most commonly used dynamometers. Eddy current dynamometers offer a fast rate of load change for rapid load stabilization. Most are air cooled, but some are designed to require external water cooling.
  Eddy current dynamometers require an electrically conductive core, shaft, or disk that moves through a magnetic field to produce resistance to movement. Iron is a common material, but copper, aluminum and other conductive materials can also be used.
  Sophisticated EC systems allow steady-state operation at controlled acceleration rates.
  In addition to their use on engine dynos, eddy current brakes are mandatory on heavy vehicles to provide endurance braking, especially in mountainous or frequent stopping situations.

 

• Hysteresis dynamometers use a magnetic rotor which is driven by the flux lines generated between the magnetic pole pieces. The magnetization of the rotor thus evolves around its B-H characteristic, dissipating energy proportional to the area formed between the flux lines.
  Unlike eddy current brakes, which develop no torque at standstill, the hysteresis brake develops a largely constant torque, proportional to its magnetizing current (or magnet force in the case of permanent magnet units) over its entire speed range.
  Hysteresis and eddy current dynamometers are two of the most useful technologies in small dynamometers (150 kW and less).

 

• A powder dynamometer is similar to an eddy current dynamometer, but a fine magnetic powder is placed in the air gap between the rotor and the coil. The resulting lines of flux create "strings" of metal particles that are constantly built up and separated during rotation, creating significant torque. Powder dynamometers are generally limited to lower speeds due to heat dissipation issues.

 

The engine to be tested drives a flywheel (an inertia wheel) whose inertial mass is known (calculated - The moment of inertia J=1/2 m*R² - for a full cylinder with m : the mass and R the radius of the flywheel. The energy developed is: E=1/2 J*ώ²).

The more powerful the engine, the higher the speed to time ratio. By making a multitude of measurements of the speed of the flywheel during acceleration we can calculate the torque and power of the motor.

The flywheel is associated with a brake which is used to stop it at the end of the test. It is also used during the engine warm-up phase to prevent the engine from being driven by the flywheel. This brake is not associated with the measurement as is the brake bench.

 

If there are ways to measure the power, the inertial and the braked. The dynos can often do both knowing that the inertial is the most widespread. Brake dynos have the advantage of being able to simulate an additional load on the vehicle in order to measure the impact of constraints (load, slope etc.).