Efficient NOX reduction with SCR on diesel engines by AVL PLUrea™

AVL PLUrea™ is a system solution for dynamic urea consumption measurement in SCR system development and application for diesel engines.

AVL Approach

Efficient NOx reduction with an SCR system requires accurate urea dosing strategy development. An individual dosing calibration is required for each specific engine and catalyst combination. Therefore online urea flow is an important parameter to be measured on an engine test bed. Accurate results are required under stationary conditions as well as during highly dynamic test cycles with transient flow rates. Extremely low urea flow rates, about 10g/h, must be measured under pulsating pressure conditions. The unique PLU measuring principle is ideal for this condition, with pressure pulsation caused by the low frequency urea injection.

AVL PLUrea™ delivers online AdBlue© consumption data for

  • System monitoring on engine and chassis test beds
  • Injector and system testing in laboratory and test bench environment (stationary)
  • Calibration of SCR-map
  • Verification of dosing models in emission and test cycles (transient)

Benefits at a Glance

  • Efficient dosing strategy development and SCR system application with dynamic consumption measurement
  • ISCR system function and performance monitoring
  • Easy testbench integration and flexible use due to mobility

AVL PLUrea™ Urea Consumption Measurement System_FU.jpg


As a system solution AVL PLUrea™ offers the following features and capabilities:

  • Integration into test bed automation or stand-alone operation.
  • Automatic air purge system provides bubble-free dosing and urea solution measurement even at extremely low flow.
  • Comfortable diagnostic and maintenance functions e.g. for media change provide for short setup time and use- friendly control in automatic engine test bench operation.
  • Compatible with all common SCR systems from passenger cars to off-road.
  • Flexible use in different locations due to mobility.
  • Fast integration, high reliability and simple use.

These features make PLUrea™ a standard tool in SCR applications on engine and chassis testbeds.

Technical Data

Technical Details AVL PLUreaTM
Urea Consumption Measurement System



Measurement principle:


Measurement ranges:

0.05 ... 10 l/h or 0.05 ... 20 l/h

Measurement uncertainty:

0.2% (acc. to DIN 1319) *)

Interfaces / output signal:

RS 232 with AK-protocol

Analog 0…10V (option)

Frequency (up to 150 kHz) TTL

Measurement frequency:

20 Hz

Response time:

< 250 ms

Fuel types:

Aqueous urea solution acc. to  ISO22241 2008/9 (Ad-Blue®); deionized water with 1% prevox 7400 (99/1%) or 50% ethylene glycol (50/50%)

Media density:

0.99 … 1.19 g/cm³

Operating temperature:

+10 … +60° C

Operating pressure:

0.01 … 10 bar; differential pressure drop Δp=0

Voltage supply:

100–240 V AC 50/60 Hz

Power consumption:

Typ. 50 W, max. 150 W

Dimensions (W x H x D):

600 x 600 x 1,700 mm

Weight (empty):

50 kg

 *) 0.3% for total consumption between 3 g and 3 kg in dynamic cycle (ETC, FTP, etc.)

Measuring Principle

AVL PLUrea™ combines the most suitable measurement technology for this application with easy handling and high reliability.

The PLU measurement principle of a servo-driven displacement counter offers the following advantages:

  • Extremely large measuring range of 1:1000
  • High accuracy even at very low flow rate <10 g/h
  • No pressure drop (Δp=0) and thereby no interference with the SCR system
  • No leakage over the gear counter due to zero pressure drop (Δp=0)

PLU Measurement Principle
The PLU positive displacement meter combines a servo-controlled gear counter with a dynamic piston sensor. A gear meter (2) driven by a servo motor (7) with encoder (8) defines a geometric volume to pulse frequency ratio when gear rotation is adjusted to media flow. A bypass (5) ensures zero pressure difference (Δp=0) between inlet and outlet, preventing leakage flow. Flow changes immediately displace a zero-friction piston (4) in either direction. A piston position sensor (3) and a servo controller (9) provide a fast gear speed control loop keeping the piston centered.