Engine test stand
An engine test stand is a facility used to develop, characterize and test engines. The facility, often offered as a product to automotive OEMs
Original Equipment Manufacturer
An original equipment manufacturer, or OEM, manufactures products or components that are purchased by a company and retailed under that purchasing company's brand name. OEM refers to the company that originally manufactured the product. When referring to automotive parts, OEM designates a...

, allows engine operation in different operating regimes and offers measurement of several physical variables associated with the engine operation.

A sophisticated engine test stand houses several sensors (or transducers), data acquisition
Data acquisition
Data acquisition is the process of sampling signals that measure real world physical conditions and converting the resulting samples into digital numeric values that can be manipulated by a computer. Data acquisition systems typically convert analog waveforms into digital values for processing...

 features and actuators to control the engine state. The sensors would measure several physical variables of interest which typically include:
  • crankshaft
    The crankshaft, sometimes casually abbreviated to crank, is the part of an engine which translates reciprocating linear piston motion into rotation...

    Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....

     and angular velocity
    Angular velocity
    In physics, the angular velocity is a vector quantity which specifies the angular speed of an object and the axis about which the object is rotating. The SI unit of angular velocity is radians per second, although it may be measured in other units such as degrees per second, revolutions per...

  • intake air and fuel consumption rates, often detected using volumetric and/or gravimetric measurement methods
  • air-fuel ratio
    Air-fuel ratio
    Air–fuel ratio is the mass ratio of air to fuel present in an internal combustion engine. If exactly enough air is provided to completely burn all of the fuel, the ratio is known as the stoichiometric mixture, often abbreviated to stoich...

     for the intake mixture, often detected using an exhaust gas oxygen sensor
  • environment pollutant concentrations in the exhaust gas such as carbon monoxide
    Carbon monoxide
    Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...

    , different configurations of hydrocarbons and nitrogen oxides, sulfur dioxide
    Sulfur dioxide
    Sulfur dioxide is the chemical compound with the formula . It is released by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide unless the sulfur compounds are removed before burning the fuel...

    , and particulate matter
  • temperatures and gas pressures at several locations on the engine body such as engine oil temperature, spark plug
    Spark plug
    A spark plug is an electrical device that fits into the cylinder head of some internal combustion engines and ignites compressed fuels such as aerosol, gasoline, ethanol, and liquefied petroleum gas by means of an electric spark.Spark plugs have an insulated central electrode which is connected by...

     temperature, exhaust gas
    Exhaust gas
    Exhaust gas or flue gas is emitted as a result of the combustion of fuels such as natural gas, gasoline/petrol, diesel fuel, fuel oil or coal. According to the type of engine, it is discharged into the atmosphere through an exhaust pipe, flue gas stack or propelling nozzle.It often disperses...

     temperature, intake manifold pressure
  • atmospheric conditions such as temperature, pressure, and humidity

Information gathered through the sensors is often processed and logged through data acquisition systems. Actuators allow for attaining a desired engine state (often characterized as a unique combination of engine torque and speed). For gasoline engines, the actuators may include an intake throttle actuator, a loading device for the engine such as an induction motor
Induction motor
An induction or asynchronous motor is a type of AC motor where power is supplied to the rotor by means of electromagnetic induction. These motors are widely used in industrial drives, particularly polyphase induction motors, because they are robust and have no brushes...

. The engine test stands are often custom-packaged considering requirements of the OEM customer. They often include microcontroller
A microcontroller is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals. Program memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a typically small amount of RAM...

-based feedback control systems with following features:
  • closed-loop desired speed operation (useful towards characterization of steady-state or transient engine performance)
  • closed-loop desired torque operation (useful towards emulation of in-vehicle, on-road scenarios, thereby enabling an alternate way of characterization of steady-state or transient engine performance)

Engine test stand applications

  • Research and Development of engines, typically at an OEM laboratory
  • Tuning of in-use engines, typically at service centers or for racing applications
  • End of production line at an OEM factory

Engine testing for R&D

Research and Development activities on engines at automobile OEMs have necessitated sophisticated engine test stands. Automobile OEMs are usually interested in developing engines that meet the following threefold objectives:
  • to provide high fuel efficiency
    Fuel efficiency
    Fuel efficiency is a form of thermal efficiency, meaning the efficiency of a process that converts chemical potential energy contained in a carrier fuel into kinetic energy or work. Overall fuel efficiency may vary per device, which in turn may vary per application, and this spectrum of variance is...

  • to improve drivability and durability
  • to be in compliance to relevant emission legislation

Consequently, an R&D engine test stands allow for a full-fledged engine development exercise through measurement, control and record of several relevant engine variables.

Typical tests include ones that:
  • determine fuel efficiency and drivability: torque-speed performance test under steady-state and transient conditions
  • determine durability: aging tests, oil and lubrication tests
  • determine compliance to relevant emission legislations: volumetric and mass emission tests over stated emission test cycles
  • gain further knowledge about the engine itself: engine mapping exercise or development of multidimensional input-output maps among different engine variables. e.g. a map from intake manifold pressure and engine speed to intake air flow rate.

Magnifying LDV sensors in Engine testing

Laser technology adds useful tools to improve engine design during engine testing. Lasers sensors using Laser Doppler Velocimetry
Laser Doppler velocimetry
Laser Doppler Velocimetry , also known as Laser Doppler Anemometry , is the technique of using the Doppler shift in a laser beam to measure the velocity in transparent or semi-transparent fluid flows, or the linear or vibratory motion of opaque, reflecting, surfaces.-Technology origin:With the...

 with Magnifying LDV sensors can record the movements of gas particles during the entire 2-, 4-stroke or rotary combustion cycle. These Spark Plug Velocimeter (SPV) sensors can be inserted into the spark plug hole of the combustion chamber of the engine. The sensors can be adjusted to all depth levels of the pistons movement - typically ranging from 0 - 50mm.
The Magnifying LDV sensors will record the velocity and direction of the movement of gas particles. Engine design can then be optimised with the recorded data and the visualisation of the combustion cycle. The flow and direction of the gas particles can be improved by changing shape and sizes of the chamber, valves, spark plug, injectors and pistons resulting in improved combustion and performance and in reduced emissions.
Engine heads with two spark plug holes per cylinder can be used to record the velocity and direction of the movement of gas particles in an engine running under live, firing conditions.
SPVs can also be added to the intake and the exhaust to record flow of particles in these areas to further improve engine design.
Magnifying LDV sensors have been used in even more extreme situations to measure particle flow in rocket engines.

See also

  • Air flow meter
    Air flow meter
    An air flow meter, is a device that measures how much air is flowing through a tube. It does not measure the volume of the air passing through the tube, it measures the actual speed of the air flowing through the device in a defined time segment. Thus air flow meters are simply an application of...

  • Driveshaft
    A drive shaft, driveshaft, driving shaft, propeller shaft, or Cardan shaft is a mechanical component for transmitting torque and rotation, usually used to connect other components of a drive train that cannot be connected directly because of distance or the need to allow for relative movement...

  • Dynamometer
    A dynamometer or "dyno" for short, is a device for measuring force, moment of force , or power. For example, the power produced by an engine, motor or other rotating prime mover can be calculated by simultaneously measuring torque and rotational speed .A dynamometer can also be used to determine...

  • Emission standard
    Emission standard
    Emission standards are requirements that set specific limits to the amount of pollutants that can be released into the environment. Many emissions standards focus on regulating pollutants released by automobiles and other powered vehicles but they can also regulate emissions from industry, power...

  • Emission test cycle
    Emission test cycle
    An emission test cycle, also known as a 'smog check', is a specified procedure for measuring pollutant emissions of engines. For emission measurements to be comparable for different engines in a category, the measurements are performed under a specific operating pattern, or 'test cycle' of...

  • Driving cycle
    Driving cycle
    A driving cycle is a series of data points representing the speed of a vehicle versus time.Driving cycles are produced by different countries and organizations to assess the performance of vehicles in various ways, as for example fuel consumption and polluting emissions.Fuel consumption and...

  • Engine cart
    Engine cart
    An engine cart is an engine support on rollers used at an engine test stand.For example, the combustion engine is mounted on this mobile support for holding the engine in an accurate position during the test....

  • Electromagnetic brake
    Electromagnetic brake
    An eddy current brake, like a conventional friction brake, is responsible for slowing an object, such as a train or a roller coaster. However, unlike electro-mechanical brakes, which apply mechanical pressure on two separate objects, eddy current brakes slow an object by creating eddy currents...

     Article about eddy current
    Eddy current
    Eddy currents are electric currents induced in conductors when a conductor is exposed to a changing magnetic field; due to relative motion of the field source and conductor or due to variations of the field with time. This can cause a circulating flow of electrons, or current, within the body of...

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