The turbocharger succumbs to the pressures of energy conservation

The turbocharger succumbs to the pressures of energy conservation

by | Wednesday, 1 July, 2020 | Automotive

For many years turbochargers were only found on expensive sports cars and diesel powered engines, but emissions regulations changed the way the world viewed forced induction. Although at the core was still the quest to improve performance, now manufacturers were looking at restoring performance and driveability to downsized fuel-sippingengines. So in the 21stCentury, almost everything from the little 999 cm3 Ford Ecoboost to the latest Ferrari’s all gained shiny new turbo technology.

But almost as soon as the tech came into its own it seems set to become redundant, upstaged by the new eCharger. Already Audi’s fitted this to the series production SQ7 and will be rolling out the technology to future production vehicles as 48 Volt electrification gains traction.

The key advantage to the electrically driven supercharger is that, as with turbochargers, there are no parasitic losses; but unlike most turbo’s there’s no turbo lag either and no need for a wastegate. The powerful electric motor can spool up the impeller to 70,000 rpm in less than a second, which eliminates turbo lag.

This naturally improves driveability and reduces consumption and emissions by between 7 and 20 percent when the device is used on a vehicle equipped with regenerative braking, which captures the car’s kinetic energy and turns it into electricity.

Pressure is key to unlocking the eCharger’s performance

Electronically controlled, the eCharger can be mapped to optimize engine performance while maximizing the energy recovered from the exhaust gas, but in order to achieve this Utopia, engineers need to create a map of the boost the engine requires by measuring manifold pressures at various engine loads and speeds. This can only be done with the aid of top quality pressure sensors.

As with any super/ turbo-charger, it’s important that the unit is matched to the engine’s requirements: Failing to do this, will either starve the engine or result in unnecessary electrical power consumption.

Being a maturing technology, not much research and testing data is available to engineers wishing to explore the boundaries of eCharge superchargers. Although fluid dynamics and electrical engineering can provide good foundations from which to build, it’s still vital that theories are validated under real-world test conditions.

In order to qualify the performance, once the baseline eCharger has been selected, the vehicle is equipped with extremely accurate pressure sensors that are readily calibrated and provide precise readings over a wide range of manifold boost pressures and temperatures. These sensors must also be resistant to vibration and chemical degradation.

Both on the engine dynamometer as well as road testing, throttle position/ engine speed/ Manifold air Pressure and temperatures are continuously recorded to ascertain the interrelationship of these key inputs.

From this information, engineers are able to verify that the correct eCharger configuration has been selected whilst at the same time ensuring that the closed loop engine management controls are able to correctly respond to the key variables.

The result of getting this right delivers a vehicle, such as the SQ7, which has stunning performance, drive ability and fuel consumption whilst still meeting future global emissions regulations.

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Manufacturers are feeling the pressure

Manufacturers are feeling the pressure

by | Wednesday, 1 July, 2020 | Automotive

With emissions regulations set to ratchet up a notch in China, Europe and North America, manufacturers are hard-pressed to optimize every engine component and function to cost effectively meet the new demands.

Although engines that are under development have always been tested to ensure they meet the most stringent quality requirements in terms of materials, emissions and efficiency, there’s a renewed focus on detailed development to unlock performance that may have previously been overlooked.

In order to do this, every time an engine is run on a test bench all the variables influencing emissions and performance have to be monitored and measured to understand their individual performance as well as how they function as part of the overall system.

This requires highly dependable, precise measuring equipment that delivers accurate readings under the extreme conditions encountered in and around the engine. Sensors of this quality and accuracy are manufactured by only a handful of suppliers around the world, which are standing out for the ability to customize quality pressure sensors to the customer’s requirements.

Pressure sensors are key to eliminating inefficiencies

STS have developed pressure sensors that meet OEM, first tier and specialist engine designers’ requirements in engine development. Using these sensors customers carry out development and design work that focuses primarily on reducing exhaust emissions and achieving a high power density, low fuel consumption, long service life and maximum reliability.

Because an engine’s efficiency depends largely on airflow and charge density into the combustion chamber and how the exhaust gases are either used to enhance the engine’s torque, by way of a turbocharger, or are able to be discharged efficiently, accurately mapping key pressure regions is critical. These pressures are often of the order of millibars, requiring extremely accurate and highly dynamic measurement.

Furthermore to obtain a reliable analysis of pressure distribution within the inlet manifold, it is important to take inlet pressure measurements as close as possible to each inlet valve. This is to accommodate the varying geometry of the manifold which often results in each cylinder being supplied with a different amount of air, which negatively impacts both performance and emissions.

When determining the performance of the exhaust system, pressure measurement becomes quite complex, as not only does the performance of the exhaust rely on pressure but also the interaction of the exhaust-gas pulses due to the engine’s firing order. STS pressure sensors are capable of measuring these processes on both the inlet and outlet sides with a high level of accuracy.

Robust sensors must remain accurate in a hostile environment

In the test environment the sensors must be resistant to the chemicals and oils associated with engines, and be able to accurately measure pressures in extreme temperatures. Moreover, the sensors need to operate reliably and not be affected by vibration or voltage fluctuations.

STS’ range of sensors also allows customers to take measurements in critical systems such as oil, fuel and water pumps, injector lines, intercoolers, and heat exchangers. All of which are vital in optimizing engine efficiency.

So although customers and regulators are increasing the demands for cleaner and better performing engines, OEMs and suppliers are well equipped to stretch the envelope and even exceed expectations.

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Bringing pressure to bear on the “camless” engine

Bringing pressure to bear on the “camless” engine

by | Wednesday, 1 July, 2020 | Automotive

Driven by draconian regulations calling for reduced exhaust gas emissions and improved fuel economy, manufacturers are spending a lot of time improving the combustion process: They’ve tried opening the inlet valves early (Referred to as the Miller Cycle), they’ve tried closing them later (Commonly referred to as the Atkinson Cycle), and they’ve even tried to create a hybrid spark/ compression ignition engine (Homogeneous Charge Compression Ignition) –all with limited success.

The problem is that these variations of the Otto Cycle engine are only effective under very specific operating conditions, which means that to maintain the engine’s performance over a wide operating range Variable Valve Timing is essential – and not only must the timing be variable on demand but it needs to be almost infinitely variable: A tall order for current Internal Combustion Engines with mechanical valve trains!

As a camshaft normally has only one lobe per valve, the valve duration and lift is fixed. And while many modern engines use camshaft phasing, adjusting the lift and valve duration during operation has limited success.

Some manufacturers use systems with more than one cam lobe, but this is still a compromise as only a few profiles can be in operation at once.

Replacing the camshafts with pneumatic-hydraulic-electronic actuators

This is not the case with the camless engine, which uses a pneumatic-hydraulic-electronic actuator to replace the traditional camshaft-based method of controlling valve operation in an internal combustion engine. This results in a much more precise and completely customizable control over valve duration and lift, on both the intake and exhaust sides: Lift and valve timing can be adjusted freely from valve to valve and from cycle to cycle. It also allows multiple lift events per cycle and, indeed, no events per cycle—switching off the cylinder entirely.

But while this system offers complete control of inlet and exhaust functions, as well as being more compact and reducing mass (On an inline 4 cylinder – 20 kilograms in mass, 50mm in height and 70mm in length), precise control of the pneumatic and hydraulic pressures are crucial for the effective operation of the system.

Mapping the pressure during development.

In order to map out the operating pressures required to operate the valves at various engine speeds and loads it’s vital that the pressures are accurately measured in real time.

This is in itself no mean feat: Not only must the pressure sensors used, be accurate over a wide range of operating temperatures, but they must be compact, vibration resistant and be able to withstand exposure to hot engine oil and other chemicals typically found in an engine compartment.

With only a handful of suppliers across the world capable of supplying high quality laboratory-grade pressure transmitters it’s important that any development team mapping out a camlessvalvetrain choose sensors with a proven track.

With this technology it’s important that both the pneumatic pressure, used to actuate the valve opening/ closing, and the hydraulic pressure, which acts as a damper as well as holding the valve open, are accurately mapped during development.

These mapped pressures will be controlled by way of an Electronic Control Unit that will determine lift, acceleration and duration depending on the engine load, speed and ambient conditions.

If the development team get the mapping of this complex process right, the rewards are quite spectacular: It’s possible to extract over 170 kW and 320Nm of torque from a 1.6-liter, four-cylinder unit which equates to 47 percent more power and 45 percent more torque than an equivalent engine equipped with a camshaft, while improving gas mileage by 15 percent.

So while camshafts have been at the heart of four stroke engine performance for over a century, valves operated by way of hydro-pneumatic pressure could well raise the ICEs game in the near future.

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